Using VNAV on an Approach
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- เผยแพร่เมื่อ 19 ก.ย. 2021
- One of the terrific features available in the latest digital autopilots is VNAV, or vertical navigation. If you have a Garmin GTN-series navigator and a GFC 500 or GFC 600 autopilot, you can use VNAV to descend to the charted altitudes along the intermediate legs of an instrument approach, until you reach the final approach fix.
This 10-minute video demonstrates how VNAV can help you fly a smooth, precise descent prior to the FAF. The video explains the basic concepts, uses the Garmin PC Trainer Suite to highlight key details, and then shows VNAV at work as I fly the RNAV (GPS) RWY 12 approach at Kelso, WA (KKLS).
For more information and links, see my blog: bruceair.wordpress.com/2021/0...
bruceair.wordpress.com/2020/0... - ยานยนต์และพาหนะ
I've been learning about VNAV functionality through videos like yours, and this is a really good one. Thanks for walking through all the details and the Garmin trainer!
I'm glad you found the video helpful. I have a couple of similar videos on my channel, and you'll also find articles at my blog: bruceair.wordpress.com/2022/12/17/using-vnav-on-an-approach/
The free Garmin PC Trainer is a terrific resource.
Very nice video. I just got an upgraded panel with G600txi / GTN750xi and GFC600 in my TBM700. I flew a test approach "old school" with the step downs and came home knowing there was a better way.... VNV + APR :) Wonderful.
Another excellent instructional video, Bruce. Thank you!
What a gorgeous day to be flying!
I’m about to head out and do this same approach in my 1960 Comanche 250! I just got dual G5’s, a 650xi, and a GFC-500 installed and will probably be making plenty of stops at Kelso, while I’m based at Pearson - KVUO. Thanks for the video!
Thank you…
Super helpful, thank you!
To make sure I'm getting it right: i could set VNAV to do the initial part of the approach and then, once i hear something like "maintain XXXft until established, cleared approach" i would ALSO press APR so the VNAV brings me to the FAF&GP and there switches by itself? (Note: i am thinking of GFC500+GTN650xi).
Again, thank you, really helpful video.
If you're an AOPA member, see my article about VNAV: www.aopa.org/news-and-media/all-news/2023/august/flight-training-magazine/instrument-tip-using-vnav-on-approach
@@BruceAirFlying great article, thank you!
Hi Bruce, what about using VNAV for the stepdown fixes on an non-precision approach? If I'm not mistaken the GFC-500 will descend to the appropriate altitudes as long as it's in the flight plan correct? Or do you have to re enter the altitude after passing each fix for the new fix. I haven't seen any videos on using VNAV for a non precision GPS approach (eg. KDLS RNAV (GPS)-A).
VNAV is available only outside the FAF. It will provide a smooth descent through the intermediate stages of an approach (precision (3D) or non-precision (2D); doesn't matter).
From the FAF to the MAP, if you're flying a 2D approach straight-in with a modern GPS, you'll probably have an advisory vertical glidepath. In fact, the GTNXi navigators provide +V advisory glidepaths even when you fly a VOR approach. But that's not VNAV. An approach with circling-only minimums (such as the example you cite) won't have advisory vertical guidance. You could use VS mode to set an appropriate descent rate along the final approach segment and change both the target altitude and VS to ensure that you meet any stepdowns inside the FAF. But again, that's not VNAV.
How did you get the GFC in the trainer? I only see options for GTN and a display.
The Garmin PC Trainer doesn't include simulation of the GFC 500 or GFC 600. To help illustrate autopilot functions in videos, I sometimes (as in this case) add still images of the autopilot controller and edit the data fields to match what should be showing in the displays. I continue to ask Garmin to include simulation of the GFC APs in the trainer; those simulations would make it much easier to train folks who have those APs.
What is the name of the panel with the heading, altitude, baro knobs. Is That an additional panel to the autopilot?
That is an optional control unit that you can install with the GFC 600 if you want dedicated knobs for ALT, HDG, etc.
How or where did you get the GFC autopilot controller for the Garmin trainer?
The Garmin PC Trainer Suite doesn't include a full emulation of the GFC 500 or 600 autopilot. I have been asking Garmin to include those boxes, but so far, no luck.
I just combined images of the avionics in my aircraft to complement the narration, which was discussing the equipment installed in my airplane. It wasn't a description of the PC Trainer Suite.
But you can kludge behavior of the GFC series in the Garmin Trainer. Select the GS option on the controller in the simulation. That tracks the VNAV vertical paths and then the GS or GP markers.
To fly VNAV and then automatically switch to GP or GS on an approach, as you join a published segment, select the altitude at the FAF with the ALT bug on the PFD, and the simulation will act like a GFC, as you see in the video that I made.
To fly VNAV on a STAR, as you join a published segment, set the ALT bug to the lowest altitude on the procedure and press GS on the simulation controller.
@@BruceAirFlying thanks for the reply. I thought that you had found something I was missing.
What does that cyan polygon around the aircraft on the map at 3:46 mean?
I think you're referring to the glide range ring, a feature available with the GTN 750Xi.
Thank you. Very good video to learn from. Until my flight yesterday I thought altitude bug had to be set to MDA/DA in order for GFC-500/600 to descend in VNAV/APP mode. Flew the KAST RNAV 26 Approach where GFC500 flew below my altitude bug in VNAV (forgot to set bug to MDA/DA). I was quite surprised it still descended. Again, thank you.
I am glad the video was helpful. It's important to understand descending with VNAV isn't the same as using APR mode to follow approved or advisory vertical guidance along the final approach segment. VNAV is an aid to flying the profile of a STAR or to fly the published altitudes along intermediate segments of an approach prior to the FAF. That's one reason the two features have separate buttons on the AP.
Is VNAV for VFR flights or IFR flghts?
As described in this video (and a couple of others on my channel), VNAV is used primarily while flying the initial stages of an instrument approach. You can use VNAV when flying VFR, for example, to help you descend to remain below the shelves of Class B airspace and to make a graceful arrival to the VFR traffic pattern at an airport.
"If you have a Garmin GTN-series navigator and a GFC 500 or GFC 600 autopilot, you can use VNAV to descend to the charted altitudes along the intermediate legs of an instrument approach, until you reach the final approach fix."
This is not true with the GFC 500. With the GFC 600, VNAV will take the airplane to the point of GP/GS intercept. This will also allow having two armed vertical modes: GP/GS and ALTV. (GP/GS is achieved by selecting APR mode.) GFC 500 will take you to a fix prior to GP/GS intercept.
Why? In the GFC 500, Transition to Approach is not enabled in the configuration mode in the GTN XXX; it is enabled in the GFC 600. I asked Garmin why: “it requires additional testing and proper documentation”. I did offer my Mooney with the GFC 500 for “testing” but at this time, a very low priority for Garmin.
You're correct that the GFC 500 does not (at present--the capability might be added later) support simultaneously arming VNAV and APR modes, like the GFC 600. You can use the VNAV feature in the GFC 500 to descend to the the altitude charted at the fix prior to the FAF and then arm APR mode, or as you observe the GP or GS indicator descending toward the center of the index, select APR mode to intercept the GP or GS.
Multiple vertical modes have now been added to the GFC500 via G5, GI275 and G3X Touch software updates.